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Questions tagged [spectral]

11 questions
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Generating and Combining Spectral Colors

I have two somewhat related questions to ask: What is the most accurate way to get the colors of a spectrum, without having to go deep into physics and simulating the universe? ;) Right now, I'm using these color matching functions, and simply…
Daniel Kareh
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Does a constant reflection over the light spectrum lead to grayscale value?

I'm currently fighting with the spectrum->RGB color conversions, my algorithm seems to make an error somewhere, e.g. I get values >1 for some spectral responses. Now there is a way to calculate an rgb value for normal incidence from index of…
Tare
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How is Iridescence handled in a Path Tracer?

I have little knowledge of this topic but from what I gather in a Ray Tracer each ray is given its own wavelength as opposed to an RGB value. This automatically simulates Dispersion and Fluorescence. Is this called Spectral Rendering? What are the…
Arjan Singh
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Hero wavelength multiple importance sampling

I want to add spectral rendering and dispersion to my pathtracer. I found the Hero Wavelength paper but I have trouble implementing this. This is how I understand the process and where I am stuck: When generating a ray, randomly sample a hero…
lyinch
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Determining input color space primaries from spectrum data

If I have an output device, for which I have a known spectrum data for each of it's primaries, I should be able to calculate the CIEXYZ of its primaries using using the integral equations together with the CIE color matching functions. I can then…
JonnyRobbie
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Reddish tint with spectral renderer

I'm trying to implement a spectral path tracer and comparing results from my program with renders of the same scene done with pbrt and mitsuba. The scene is just some spheres in a box with one point light. All the surfaces have simple Lambertian…
Kirill Dmitrenko
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Computing sRGB color from SPDs

I'm trying to write my own spectral path tracer and a bit stuck with converting computed SPDs to LDR RGB values. What I'm doing right now is convert sampled SPDs (in W/m^-1) to XYZ using CIE 1931 color matching functions: Vec3 xyz(0, 0, 0); float…
Kirill Dmitrenko
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Does CIE XYZ preserve spectral accuracy when used for progressive rendering?

How accurate it is to estimate rendering equation using wavelengths and then convert result to CIE XYZ to accumulate samples temporally by averaging them over time?
Ocelot
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How to determine RGB values given a display spectral response curve?

I am reading Physically Based Rendering section 2.2.2 on RGB color. I am trying to understand how, given a display spectral response curves for rgb intensities, we can choose the intensities so that the display will emit an equivalent spectrum (a…
Elad Maimoni
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Is spectral response curve and spectral power distribution the same thing?

I'm reading section 5.2 of pbrt 3rd edition and came across the part where they explain the concept of RGB colors. When we display an RGB color on a display, the spectrum that is actually displayed is basically determined by the weighted sum…
Peter
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How to calculate spatial frequency of an image just in one direction?

FFT spectra is not what is needed; what I need is a histogram showing which frequencies are there in image in horizontal direction, and which one is dominant Such spatial frequency is usually known for a sinusoidal grating; I need the same property…
ivan866
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